Some notes I've been keeping about this and meaning to share when they made more sense. I guess I'll share them anyway, since I don't seem to be working on this anytime soon. May or may not be good ideas.

• ToolGroups should fully manage their tools, Tool shouldn't generate any elements
  • Possibly Tool should be gone, user would instead provide plain object configuration
• Get rid of confusion between 'title' and 'label'
• Remove use of 'updateState' for internal updates (MenuToolGroup)
• Remove setting tools as active on click
  • Tools that can be active and those that can not should be separated
• Remove need for nested toolbars - way to place a separator

Thanks!

• ToolGroups should fully manage their tools, Tool shouldn't generate any elements
  • Possibly Tool should be gone, user would instead provide plain object configuration

I think T309197 is similar to this.